This invention relates generally to valves and specifically to a design of valves used for evaporative cooling applications.
Evaporative cooling techniques in one form or another have been used for centuries. The concept is to pass a stream of hot relatively dry air over a surface of water (usually established by moistened pads) permitting the water to evaporate and consume energy from the hot dry air; thereby cooling the air.
Systems used to wet pads in existing evaporative coolers include: a recirculating pump arrangement; once-through flow systems; and a solenoid valve-timer combination (non-recirculating system).
A recirculating system is the most common approach and is used in most evaporative ("swamp") coolers which employ blowers to move the air. Through the use of a pump, water is dumped over a cooler's pads to trickle down. Any excess water is caught in a basin. The pump recirculates this excess together with fresh water from a pressurized line over the pads.
In some applications, the electrical supply required by this approach's pumps and blowers is not available or is economically prohibitive, making this device infeasible.
In all systems, some excess of water above that which evaporates is always required to prevent scaling or salt build-up; this excess is called "blowdown", and is discharged to waste or used for plant irrigation.
Perhaps the oldest and most wasteful of the water depositing systems is a once-through system which either pumps or discharges water continuously from a pressurized line over the pads. This "once-through" system is quite wasteful of water. If the water flow is reduced to a point where it barely exceeds evaporation, "channeling" occurs, with uneven wetting of the pads, dry spots, loss of efficiency, and salt build-up.
As can be quickly appreciated, this approach is extremely wasteful of water since a constant flow is required that is relatively unregulated and totally ignorant of the changing environmental conditions..
The third approach which has been used is where an intermittent flow of water to the pads is used. The flow of water is cut on and off periodically using a timer-solenoid valve combination. With this system, specialized pads must be used which are readily wetted which retain water well. Some such pads include: Cel-Dek which is commercially available from Munters Corp., Fort Myers, Fla.; or Glacier-Cor from Eng-Cor Inc, La Mirada, Calif.
In this application, the water must flow over the pads at a substantial rate during the "on" portion of the cycle to assure complete wetting and flushing of air borne dust or debris. The ratio of time off to time on is approximately 20:1 or 25:1.
Again, because a solenoid is used, this approach of a timer-solenoid valve requires the availability of electricity.
It is clear from the foregoing that an electricity independent system does not exist for evaporative cooling applications.